Vibration-damping material



Patented May 23, 1939 VIBRATION-DAMPING MATERIAL Herman H. Nies,Waukegan, Ill., assignor to Johns-Manville Corporation, New York, N. Y.,a corporation of New York No Drawing. Application March 13, 1935, SerialNo. 10,959

4 Claims.

This inventionrelates to a material adapted for use in dampingvibrations of vibratile objects, such as sheet metal automobile bodiesor the like.

The need of vibration-damping for such objects 5 is evident. As aresult, a number of materials have been developed for this purpose.Thus, at one time, there was sprayed upon the metal sheet, the vibrationof which was to be damped, a mixture comprising asphalt, a vegetableoil, a light- 10 weight filler, such as cork flour, and a smallproportion of graphite, the graphite serving to promote smoothnessduring application. The mixture was made at an elevated temperature, andwas kept well stirred before use, to prevent 15; settling of thelightweight filler and graphite.

With such a spraying composition, it has been necessary to apply a thicklayer, say a layer of thickness. of the order of one-tenth inch. Withsuch a thick layer applied, for example, to a 20 vertical surface of thedoor of an automobile, the forceof gravity tending to cause flowing hasconsiderable moment, because of the distance between the center ofgravity of such a thick layer and the point of support upon the verticalsur- 25 face. Also, the cost of such a treatment increases with thethickness of layer required. Furthermore, it is not always feasible tokeep a composition well stirred between the time of original manufactureand final use, or even for the short period immediately preceding orduring the spraying process.

Recently, spraying compositions have been largely replaced, therefore,by partially saturated felts which overcome difliculties inherent in the35 spraying-compositions and which are adhered to the vibratile object.

.It is an object of the present invention to provide a vibration-dampingmaterial of the sprayon type that is more effective in thin layers, of

40 lower cost per square foot of surface damped, of greater toughnessand tenacity, and/or of lesser tendency to settling of a filler materialtherefrom than is the conventional spray material.

A preferred embodiment of the invention com- 45 prises a plastic.composition including a large proportion of fine particles ofmass-adding material of high specific gravity, dispersed predominantlyin non-contacting relationship. Another embodiment comprises such adispersion in a 50 medium that has been specially treated to minimizesettling of the heavy particles from the medium, particularly during theperiod of time from the making of the mixture or dispersion to itsapplication and hardening upon the article 55 the vibration of which isto be damped.

The invention is illustrated by the following specific example showing atypical composition and the method of making the same in accordance withthe invention.

There is first provided a yieldable plastic medium of the type of, aviscous fluid. There is provided, for example, a medium of asphalt-likematerial blown by air at an elevated temperature and for a substantialperiod of time, adapting the resulting material to give a livered orsome- What gelatinnous mixture or solution in a volatile thinnertherefor, such as a straight-run high test gasoline. Thus, there may beused, as the plastic medium, a highly blown petroleum still residue.

The plastic medium so made is mixed thoroughly with a thinner orextender such as the high test (H. T.) gasoline, this gasoline beingpreferably of substantially lower boiling range than U. S. motorgasoline.

To increase the, toughness of the film is to be produced ultimately, tomake possible the use of a more highly blown or more viscous medium, andto lower the requirement of volatile solvent at the time of applicationto the vibratile object, there is suitably incorporated a drying oil,such as linseed or China-wood oil. Preferably, the drying oil is madeinto a mixture with the asphalt like material after the latter has beenblown, as previously described. The mixture is extended with thinner.The resulting composition, including a plastic medium dissolved orextended by a volatile thinner, is suitably of the consistency of alight gel.

Into the composition there is then admixed fine particles of solidmaterial of high specific gravity and, suitably also, fibrousreenforcing material.

Finally, the whole composition is thinned, by additional volatileextender for the said medium, to the consistency desired, after whichthe composition is ready for being sprayed or otherwise applied to theobject the vibration of which is to be damped.

The proportion of granular filling material, in the form of particles ofsolid of high specific gravity, such as the grains of sand mentioned,should be large, to give a maximum vibrationdamping effect. On the otherhand, the proportion should be not so large as to prevent floating ofthe particles in the plastic medium, as will be described. A proportionof such particles comprising more than 200 per cent and notsubstantially more than 600 per cent by weight of the said medium ispreferred.

A typical composition that has been used satisfactorily is thefollowing:

Parts by Ingredients weight Petroleum still residue, in highly blowncondition 10 Boiled linseed oil 3 H. T. gasoline, to thin aboveingredients before addition of remainder of the composition 11 Asbestosfibres, short ll Sand, banding 58 Additional H. T. gasoline. 7

After the composition has been applied to the compositions of lesseroverall density. This gives an economy in the amounts of plastic mediumand volatile thinner required. Furthermore, the film of lesser thicknessminimizes the moment of the force tending to cause flowing on other thanhorizontal surfaces.

Settling is minimized, even in the presence of the particles of densefiller material, since the blowing of the asphalt-like material causesit to liver, when later mixed with the gasoline, to form a gel ofviscosity far above the range of viscosity of ordinary fluids; from sucha gelatinous composition the particles of filler settle either veryslowly or not at all.

In such a composition the particles of sand filler are preferablyrounded, as in banding sand. In place of sand, as filler, there may beused other finely divided particles of high specific gravity, as, forexample, over 2, such as particles of? slate, lead, iron or the like.The particles of heavy filler in the finished vibration-damping filmfloat in the plastic medium, that is, are discrete or predominantly innon-contacting relationship to each other. In this manner, there isobtained the effect of a composition that is very dense but thatpreserves, on the other hand, largely the yieldability of the plasticmedium selected, in distinction from the rigidity that would result frombonding together firm or hard particles in skeletonizing contact witheach other. The particles of filler used are non-colloidal andnonfiufiing, in distinction from colloidal clays and the like, and areadapted to cause a large increase in the overall density of thevibration-damping material.

As a plastic medium there may be used other bituminous material, such asnatural or artificial asphalts, stearin pitch, plastic resinous bodiesor the like.

While short fibres of asbestos are preferred as the reenforcingmaterial, rag fibres may also be used. The reenforcing material reducesthe tendency, of the plastic medium to fiow from preestablished positionon the vibratile object. The reenforcement permits the use of a mediumoriginally of such degree of yieldability as would otherwise causeflowing. At the same time, the reenforcement, being yieldable, does notdestroy the overall plasticity and vibration-damping property of themass.

The volatile thinner, represented in the tabulation above by high testgasoline, should be one adapted to preserve the desired viscous natureof the spraying composition, as by giving a livered or gelatinouscomposition on being mixed with the plastic medium, such as the blownasphalt, unless the function of prevention of settling of the fillerparticles is not desired. To make such a gel, the thinner used for theplastic medium should be an imperfect solvent. Thus, for highly blownasphalt-like material, the solvent may be gasoline, naphtha, or the likeof low aromatic content. A perfect solvent, if used, would lower theviscosity to an extent that is undesirable for best results.

It will be understood that an element of my composition or a step in thepreparation may be omitted if the function served thereby is notdesired.

It will be understood, also, that the details that have been given arefor the purpose of illustration, not restriction, and that variationswithin the spirit of the invention are intended to be included withinthe scope of the appended claims.

What I claim is: I

l. A vibration-damping material of a sprayable consistency comprisingblown asphalt, filler particles of sand, and a volatile extender that isan imperfect solvent for the asphalt and forms therewith a liveredmixture, the proportion by weight of the filler particles being between2 and 6 times that of the asphalt and the said particles beingdiscretely dispersed in the asphalt in such a manner as topreserve theplastic character of the asphalt.

2. A vibration-damping material of a sprayable consistency comprising anintimate mixture of blown asphalt, reinforcing fibres, and sand fillerparticles of high specific gravity relative to the asphalt, theproportion by weight of the filler particles being between 2 and 6 timesthat of the asphalt and the said particles being discretely dispersed inthe asphalt in such manner as to preserve the plastic character of theasphalt.

3. A vibration-damping material as described in claim 2 and including adrying oil intimately mixed with the asphalt.

4. A vibration-damping material of a sprayable consistency comprisingblown asphalt, sand filler particles, and a volatile extender that is animperfect solvent for the asphalt and forms therewith a livered mixture,the proportion by weight of the filler being between 2 and 6 times thatof

